In supercritical fluid chromatography, when a supercritical fluid of 10 MPa or more as a mobile phase, which is, for example, liquefied carbon dioxide (CO2) or a fluid in which an organic solvent as a modifier is added to liquefied carbon dioxide, is vaporized after being reduced to atmospheric pressure after passing through a back pressure regulator (BPR), the temperature drastically decreases due to the adiabatic expansion and the vaporization heat. At that time, carbon dioxide turns into dry ice, causing freezing or clogging of a pipe. To prevent this, it is practiced to heat a back pressure regulator or a pipe arranged on a downstream side of the back pressure regulator with respect to the flow of the mobile phase.
In order to prevent an outlet flow passage opening of the back pressure regulator from being clogged or broken by dry ice, it is known that a back pressure regulator itself is heated with a heater (see Patent Document 1). In Patent Document 1, there is no description that the outlet side pipe of the back pressure regulator is heated.
There is a case in which a pipe connected to an outlet flow passage of a back pressure regulator is wound around a heat exchange block provided with a cartridge heater to heat the vaporized fluid flowing through the pipe to thereby prevent freezing of the pipe (see Patent Document 2). In this case, the entire pipe wound around the heat exchange block is constantly heated.
Further, there is a case in which a cartridge heater and a trim heater are provided between a back pressure regulator and a transfer pipe to a fraction collector to completely evaporate liquefied carbon dioxide portion of the discharged fluid to thereby prevent ice formation on the outside of the transfer pipe (see Patent Document 3). Also in this example, the portion to be heated by the cartridge heater and the trim heater is fixed.